A Novel Cytoplasmic Protein That Interacts with the Ah Receptor, Contains Tetratricopeptide Repeat Motifs, and Augments the Transcriptional Response to 2,3,7,8-Tetrachlorodibenzo-p-dioxin

doi:10.1074/jbc.272.14.8878

A Novel Cytoplasmic Protein That Interacts with the Ah Receptor, Contains Tetratricopeptide Repeat Motifs, and Augments the Transcriptional Response to 2,3,7,8-Tetrachlorodibenzo-p-dioxin*

Qiang Ma and
James P. Whitlock, Jr.^‡

From the Department of Molecular Pharmacology, Stanford University School of Medicine, Stanford, California 94305-5332

^‡ To whom correspondence should be addressed. Tel.: 415-723-8233; Fax: 415-725-2952.

Abstract

To identify new proteins involved in dioxin-dependent signal transduction and transcriptional regulation, we used a yeast two-hybrid system to identify proteins that interact with the Ah receptor (AhR). We cloned a mouse cDNA, which encodes a novel ∼37-kDa protein that binds to AhR; we have designated the protein as Ah receptor-interacting protein (AIP). The amino acid sequence of mouse AIP exhibits homology with members of the FK506-binding protein family. AIP also contains three tetratricopeptide repeat (TPR) motifs; the TPR sequence is present in proteins required for cell cycle control and RNA synthesis and in steroid receptor-binding immunophilins. Coimmunoprecipitation experiments in mouse hepatoma cells reveal that AIP is cytoplasmic and associates with unliganded Ah receptor and with hsp90; 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment disrupts the AhR-AIP-hsp90 interaction. Overexpression of AIP augments the response of the CYP1A1 gene to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Our data suggest that AIP influences ligand receptivity and/or nuclear targeting of AhR.

Footnotes

↵* This study was supported by Research Grant ES 03719 (to J. P. W.) and by NRSA ES 05679 (to Q. M.) from NIEHS, National Institutes of Health. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) U85489[GenBank].
↵¹ The abbreviations used are:

AhR

aromatic hydrocarbon receptor

AIP

Ah receptor-interacting protein

Arnt

AhR nuclear translocator

FKBP

FK506-binding protein

hsp

heat shock protein

TPR

tetratricopeptide repeat

bHLH

basic helix-loop-helix

TCDD

2,3,7,8-tetrachlorodibenzo-p-dioxin

DBD

DNA-binding domain

AD

activation domain

PCR

polymerase chain reaction

kb

kilobase pair(s)
- Received November 18, 1996.
- Revision received December 20, 1996.